Automatic processing devices for processing photographic materials

ABSTRACT

PCT No. PCT/EP91/00123 Sec. 371 Date Jul. 21, 1992 Sec. 102(e) Date Jul. 21, 1992 PCT Filed Jan. 9, 1991 PCT Pub. No. WO91/10940 PCT Pub. Date Jul. 25, 1991.An automatic film processing device replenishment system where an infra red sensor is located to measure silver content of the image on a film or paper carrier, and use the measured silver content for control of replenishment of the process chemicals. In a preferred arrangement a first infra red sensor measures silver content and controls replenishment of developer and bleach and a second infra red sensor measures silver halide content and controls replenishment of fixer.

FIELD OF THE INVENTION

The present invention relates to automatic film processing devices forthe processing of photographic material.

BACKGROUND OF THE INVENTION

Various kinds of processing machinery are available for processingnegative film, for processing colour prints, for processing colourreversal film and for preparing reversal prints.

In general the process involves developing a silver image then oxidisingthe silver in a bleaching stage followed by removimg the silver in afixing stage. These stages occur in all normal photographic processes,whether black and white, or colour and whether negative or reversalprocessing; although further stages will be required in the case ofreversal processing, and dye coupling during development in the case ofcolour processing.

In automatic processing systems, ingredients are taken up in the variousstages of processing, and therefore the various processing baths needreplenishment of their constituents in order to keep them at the correctconsistency.

Automatic replenishment systems have been proposed previously in whichthe strength of the developed dye image is measured and this is thenused to determine the rate of replenishment of the various ingredients.U.S Pat. Nos. 4,057,818 and 3,554,109 describe such systems.

In these systems dye density is measured after the film is fullyprocessed in order to assess the replenishment needs.

These methods therefore give rise to a degree of inaccuracy since theamount of dye in the final image is not necessarily a direct function ofthe total amount of developing agent consumed in forming the finalimage.

The present invention directs itself to this problem and aims to providean improved method of assessing the replenishment need.

SUMMARY OF THE INVENTION

Accordingly the present invention provides an automatic film processingdevice for photographic materials including at least one developingstation to develop an image including silver on a carrier substrate, andat least one station for bleaching and removing the silver to provide afixed image on said carrier substrate, an infra red sensing device formeasuring the need for replenishment and replenishment means forreplenishment of developer chemicals in dependence on the measured needfor replenishment, characterised in that the infra red sensing device islocated at a position prior to removal of the silver and is arranged tomeasure the density of silver in the developed image on the carriersubstrate in order to provide a measure of the replenishment need.

Accordingly the infra red sensing device will normally be providedimmediately after the developing station and prior to the bleaching andfixing station or stations.

The measurement of silver can be used for control of replenishment ofdeveloper, bleacher and fixer; however replenishment of fixer can bemore accurately controlled by measurement of silver halide.

Accordingly a second feature of the present invention is provision of asecond infra red sensing device which is located to measure silverhalide content-of said carrier substrate, and thereby to controlreplenishment of fixer. In such a case the first infra red sensingdevice controls replenishment of developer and bleacher chemicals.

The carrier substrate may be a negative or transparency film base or itmay be a paper base for colour prints.

In the case of colour processing, measurement of the amount of developedsilver in situ during development is particularly accurate since theamount of colour developing agent consumed and the amount of bromide ionreleased in the development reaction is proportional to the amount ofsilver developed. This means that the replenishment need for any filmcan be accurately assessed from the average developed silver level.

On the other hand in the prior art processes where dye density ismeasured, this measurement is less accurate because the dye to silverratio can vary for different film types and from differentmanufacturers. The reason for this variation is that not all theoxidised colour developing agent generated during silver developmentgoes to form dye. A variable proportion of colour developing agentundergoes side reactions such as sulphonation and deamination.

Different films contain couplers of different activity which means theyhave different abilities to consume colour developing agent. If colourdeveloping agent is not consumed it does not form dye and is lost in oneor other of the side reactions mentioned above. Because of this the dyeto silver ratio is variable and so dye density does not necessarilyreflect silver development or replenishment needs accurately.

In addition different films contain different silver levels although thedye density aim is similar. Thus to use dye density to assessreplenishment needs would require a knowledge of the actual film type,and this is unnecessary if silver is measured directly.

Dye density will depend on the measurement apparatus and the opticalfilters used and also on the hue of the dye in the film. The dye and dyehue also vary from film to film and between manufacturers. This willcause further inaccuracy in assessing replenishment needs by means ofdye density measurement.

Coloured couplers are used in most colour negative films to provide somecompensation for the unwanted absorption of the image dyes. To make thiscompensation, the colour of the coupler is destroyed by coupling withcolour developing agent as the image dye is formed. Thus there will be avariable colour and amount of coloured coupler necessary depending onthe amount of unwanted absorption. This factor will again confuse therelationship between average dye density and amount of developed silverand thus upset the assessment of replenishment based on average dyedensity.

Some of the dye density in the minimum density areas can be due toretained sensitized dyes and not image dyes or coloured couplers. Thiswould be measured as part of the average dye density but would beunrelated to developed silver and also to replenishment needs.

The replenishment of the bleach bath is also directly related to theamount of silver it has to remove from the film. Again the replenishmentneeds are not accurately assessed from dye density because of thevariable dye to silver ratio in different films.

In addition there is the fixer bath, which removes silver halide thatwas originally unused in the development and also silver halideregenerated in the bleach bath. In this case also the replenishment needis entirely unrelated to the average dye density. A second infra redmonitor can be used to measure total silver halide and so it can providean accurate assessment of the silver load in the fixer bath andtherefore its replenishment needs.

DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described by way of examplewith reference to the accompanying diagrammatic drawings in which:

FIG. 1 is a schematic block diagram of a film processor unit; and

FIG. 2 shows an infra red sensing device.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a film processor unit essentially comprisesstations 1 for developing, 2 for bleaching, 3 for fixing and 4 forwashing of a film which passes along the path 5 through each of thebaths in turn. The process uses standard processing chemicals such asthe Kodak C41 process ingredients. Located between the developer station1 and the bleaching station 2 is a first infra red sensing device 6which is shown in detail in FIG. 2. Replenishment baths 7, 8 and 9provide replenishment chemicals to the developing station 1, thebleaching station 2 and the fixing station 3 respectively.

The first infra red sensing device 6 is located to measure the silvercontent of the film and to provide a signal via computer processor 10for control of replenishment of the baths 7 and 8 for replenishnent ofthe developer and bleach solutions.

A second infra red sensing device 11 is located between the bleachingstation 2 and the fixing station 3, so as to measure the silver halidecontent of the film and provide a signal via computer processor 12 forcontrol of replenishment of the fixer to fixing station 3.

Two alternative locations for the second infra red sensing device 11 arein the bleaching tank 2 or prior to the developing station 1, where ineach case a measure of silver halide content can be made.

The replenishment system in each case is shown in its simplest form,namely a tank feeding replenishment chemicals straight into therespective bath, but in practice in many commercial operations such asystem would be more complex. Often, an overflow, regeneration, mixingand recharging circuit would be employed and this is well known in theart.

As previously mentioned, the processor is a conventional multi-tanksystem for carrying out the Kodak process C41. This is for developmentof colour negative film. A critical feature of the invention is that theinfra red detector is located immediately after the developing stationso that it can monitor the developed silver image in order to controlreplenishment.

There are several other processes where the invention is equallyapplicable. In each of these other processes the same basic processsteps of developing then bleaching then fixing arise, whether inprocessing colour prints (the Ekta print 2 process) or in processingcolour reversal film (the process E6) where additional steps to causereversal take place or in reversal processing of prints, i.e. printsfrom transparencies (the process R3). In each of these cases theimportant factor is to locate the first infra red detector at a pointafter the development stage but before removal of the silver, and tolocate the second infra red detector at a point where silver halide canbe measured.

Referring now to FIG. 2, this shows the device 6 for sensing the infrared density of the metallic silver in the film after development. Thesecond infra red sensing device is of a similar structure.

The device comprises a support 20 which carries an infra red emittingdiode (LED) 22, and an infra red photodiode detector 26. The LED 22 andthe detector 26 are sealed in respective transparent plastics tubes 24,28 and they are spaced apart by the support 20 as shown. Film 34travelling along path 5 is arranged to pass close to the detector 26 sothat the infra red density sensed by the amount of radiation passingfrom the LED 22, through the film 34, and on to the detector 26,approximates to the diffuse density of the film. The absolute value ofthe density is unimportant.

The LED 22 is driven at a constant current from a power supply (notshown) by means of connections 30. The detector 26 is spectrally matchedto the LED 22. The wavelength of the infra red radiation emitted by theLED 22 is around 950 nm.

The detector 26, when operating in its linear short circuit currentmode, produces a signal which represents transmission of infra redradiation through the film 34. The signal from the detector 26 isconverted to a density value by a monolithic logarithmic amplifier (notshown) to provide an output signal which corresponds to the densityvalue. This signal is monitored by its computer processor 10 (seeFIG. 1) through connections 32 and is processed to provide control forreplenishment. Thus, signals from the computer 10 can then be fed toeach of the replenishment tanks 7 and 8 (these signals are shown asdouble arrows.

In the same way the signal from the second infra red detector 11 is fedvia its computer processor 12 to the fixer replenishment tank 9.

Thus, by measurement of the average silver and silver halide density ofa particular film, the amount this varies from a predetermined norm canbe used to vary the amount of replenishment chemical fed into each ofthe processing stages 1, 2 and 3.

For example it is known that for Kodak VR100 film the usage rates at anaverage customer density are as follows:

    ______________________________________                                        COMPONENT    USAGE RATE (g/ft.)                                               ______________________________________                                        CD4          0.01                                                             NaBr         -0.0045                                                          K2S03        0.0031                                                           HAS          0.0024                                                           pH           0.0011    units/ft                                               ______________________________________                                    

If then the measured density of the film is greater than the expectedaverage or less than that expected average all these component usagerate measurements are adjusted on a pro rata basis. This enables thecorrect quantity of developing agent replenishment rate to be achieved,and similarly the replenishment of the bleaching and fixing stations canbe adjusted.

While the block diagram schematic arrangement shows a single control toeach of the replenishment tanks, it is possible to design more complexarrangements where individual components are individually adjusted atdifferent rates.

The main advantages of carrying out the invention are as follows:

1. The actual silver densities for each film are obtained as opposed tosome overall trade average. This means that the replenishment calculatedfrom these values applies directly to that film and is therefore likelyto be more accurate.

2. The type of film does not have to be determined because averagedensity differences from film type to film type are automaticallymeasured. This means that there is no need for the operator to docomplex sums to determine the average film-type-mix that is beingprocessed in order to calculate the correct replenishment rate.

3. High exposure or low exposure films with non standard densities arecorrectly assessed.

4. Variable amounts of end fogging are automatically accounted for.

5. The system is fully self-contained and can be part of an automaticreplenishment control mechanism which will enable the use of loweffluent chemistry and at the same time give improved process control.

6. If this system is sufficiently accurate it might be possible todispense with control strips or at least to reduce the frequency oftheir use and thus provide a cost saving to the user.

We claim:
 1. An automatic film processing device for treatingphotographic material including:at least one developing station fordeveloping a silver image on a carrier substrate; at least one stationfor converting metallic silver to silver halide and for dissolvingsilver halide to provide a fixed image on the carrier substrate; aninfra red sensing device for measuring a parameter of the process, theinfra red sensing device being located at a position immediately afterthe developing station and prior to any subsequent station and isarranged to measure the density of the silver in the developed image onthe carrier substrate; and replenishment means for effectingreplenishment of developer chemicals according to measurement of thedensity of the silver in the developed image on the carrier substrate toprovide a measure of the replenishment need; characterized in that thedevice further comprises a second infra red sensing device located tomeasure silver halide in the carrier substrate to provide a signal forcontrol of the replenishment of the at least one station for dissolvingsilver halide to provide a fixed image on the carrier substrate.
 2. Adevice according to claim 1, wherein the at least one station forconverting metallic silver to silver halide and for dissolving silverhalide to provide a fixed image on the carrier substrate comprises ableaching station for converting metallic silver to silver halide and afixing station for dissolving silver halide, the second infra redsensing device being positioned prior to the fixing station.
 3. A deviceaccording to claim 1, wherein the at last one station for convertingmetallic silver to silver halide and for dissolving silver halide toprovide a fixed image on the carrier substrate comprises a bleachingstation for converting metallic silver to silver halide and a fixingstation for dissolving silver halide, the second infra red sensingdevice being position in the bleaching station.
 4. A device according toclaim 1, wherein the second infra red sensing device is located prior tothe at least one developing station.